Calculating Energy Delivered to a Battery using Ohm's Law

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To calculate the energy delivered to a battery, use the formula E = P · t, where power (P) is calculated as voltage (U) multiplied by current (I). In this case, the voltage is 12 V and the current is 7.5 A, leading to a power of 90 W. The time of 3.5 hours must be converted to seconds, which equals 12,600 seconds. Multiplying the power by the time gives a total energy delivery of 1,134,000 joules. This approach clarifies the correct method for calculating energy delivered to the battery.
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A battery charger is connected to a dead battery and delivers a current of 7.5 A for 3.5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

I'm not exactly sure what I am doing wrong. I understand that we have to use Ohm's Law in this question. So doing that, I took the given current, and converted it into the total number of coloumbs used over the 3.5 hours. I then calculated the resistance, and then I multiplied the total coloumbs by the resistance, and got joules (151,200). That's wrong, so I'm not sure where I went wrong.

I'd appreciate any help. Thanks.
 
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tigerguy said:
A battery charger is connected to a dead battery and delivers a current of 7.5 A for 3.5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

I'm not exactly sure what I am doing wrong. I understand that we have to use Ohm's Law in this question. So doing that, I took the given current, and converted it into the total number of coloumbs used over the 3.5 hours. I then calculated the resistance, and then I multiplied the total coloumbs by the resistance, and got joules (151,200). That's wrong, so I'm not sure where I went wrong.

I'd appreciate any help. Thanks.

use E = P \cdot t = U \cdot I \cdot t with t in seconds.
 
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